Revert "Move StagedRollbackTest from postsubmit to presubmit"

This reverts commit 0509c71cc44523af4c44b20316be96f781d52e02.

Reason for revert: Droidmonitor triggered revert due to Test breakage in b/349693967. Will be verifying through ABTD before submission.

Change-Id: I66a706b8b4f9bf802f7ea1a6b50bb4847b915c92
diff --git a/libprocessgroup/TEST_MAPPING b/libprocessgroup/TEST_MAPPING
index b713f6b..29a9ff0 100644
--- a/libprocessgroup/TEST_MAPPING
+++ b/libprocessgroup/TEST_MAPPING
@@ -1,5 +1,5 @@
 {
-  "presubmit": [
+  "postsubmit": [
     {
       "name": "StagedRollbackTest"
     }